SOT data are vital for identifying the photospheric and chromospheric roots of the loop footpoints, and measuring the vector magnetic field. A Spectro-Polarimeter (SP) observations are requested over a spatial region of 180”x164” once an hour each day, interspersed with BFI images in G-band, Ca II and H-alpha (focus optimised for Ca II).
I had an action item to look at Kelly Korreck's HOP 96 proposal, which proposed dropping the SOT telemetry allocation to 15%. Here is the response that I sent to her (unfortunately, only yesterday).
First, the easy questions about the requested SOT observations. It is a reasonable program to run for this purpose. Taking your request literally, the SP fast maps would use about 2,100 Mbits/day (340 Mbits each) and the filter images about 800 Mbits/day (assuming one set every 10 minutes). Each SP map takes about 35 minutes to make. This total telemetry, 2900 Mbits, is a little more than our normal daily allocation nowdays (70% of the total).
A reasonable fallback position might be 2 SP maps (at the start and end of the EIS observations) instead of 6 and one-quarter of the filter image total through a combination of higher than usual compression and lower cadence. This could get the SOT total down to between 20 and 25% of the typical total daily allocation.
I'm not opposed in principle to a program like this with low SOT telemetry, if the monthly meeting agrees that it is a good science priority and the telemetry is really needed by the other instruments. I would not agree to run it on the first (or 2nd or 3rd) good AR that comes along after the present drought, because SOT (and Hinode) have a number of other high priority programs which have been waiting for a good AR. But I would agree for the Nth, where we can discuss the value of N.
I will leave it to the EIS folks to estimate how much of the telemetry they really need for your program.
I also have some concern about all 3 instruments burning our entire telemetry allocations in 4 or 6 hours of the day, for 6 days in a row; I think we should hold some in reserve for capturing the evolution of the region in the remaining time and perhaps for a flare response.
Tom Berger pointed out the following:
"Is another concern about filling the DR in 4--6 hours per day for 6 days in a row is that it may require special pass management to avoid having many "blank" downloads later in the timeline?"
I'm not sure if this will cause a problem or not in pass management. My point was that the instruments should hold back a little telemetry so we are not idle for the remaining 18-20 hours per day.
Kelly replied "I am going to see if I can't rework it in a way that science is still done but that doesn't pile up the data in 6 hours. "